Sonic Adventure 2 (Japanese: ソニックアドベンチャー 2) is the second three-dimensional platformer (and third overall title) staring Sonic the Hedgehog on the Sega Dreamcast. The follow-up to its highly-praised predecessor Sonic Adventure, it also ended up becoming one of the swan songs for the system. Released shortly after Sega announced the discontinuation of the hardware and its removal from the console business, the game not only became the last Sonic title produced for a Sega system, but the first ever Sonic title ported to a non-Sega system, in the form of Sonic Adventure 2: Battle.

Story

Professor Gerald and Maria.

Fifty years ago, there was a brilliant, gifted scientist known to the world as Professor Gerald Robotnik. Though well known in his fields of study, he dedicated his life to his granddaughter, Maria Robotnik. It was because of her that he found joy in an otherwise harsh world. Because of his renowned status, the leader of the United Federation contacted the brilliant mind to assist on a research project that could change the very fate of the world: "Mankind's ultimate eternal dream, researching for immortality." Though at first he refused for fear that it crossed the limits that man should dare tamper with nature, he eventually relented when he discovered that Maria had been diagnosed with a genetic disorder known as Neuro Immunodeficiency Syndrome. Referred to as "N.I.D.S." for short, the rare disease was known to be fatal, with no cure as of yet discovered by medical science. Distraught over the idea of losing his granddaughter, Professor Gerald reversed his decision, telling the President that he would indeed assist in the quest for immortality, hoping to use the research to find a cure for Maria.

The grandfather and daughter pair were soon shuttled into space to live aboard the Space Colony ARK, a Bernal-sphere space station designed to hold numerous research facilities and double as a living area not just for the researchers and military personal who worked aboard, but for their families as well. Once on-board, Professor Gerald began work on "Project Shadow," code-named as such because of the many people who felt that what Gerald was working on was just as intangible as a shadow.

The first order of business that Gerald tackled was to study the mysterious gems known as the Chaos Emeralds, wanting to see how their infinite energy could be applied to living things. The result of this research were the Chaos Drives, specially designed to have artificial energy be applied to a variety of objects, from military-approved robots to living tissue. With the experimental drives ready for use, "Project Shadow" was finally ready to begin its next phase - the creation of the "Ultimate Lifeform." Initially starting out with a prototype design, the creature the research team hoped to bring to life started out as a lizard-esque being. Later named the Biolizard, the Chaos Drives helped bring it to life on the 27th of January, the entire team celebrating at their success. Being the first man-made artificial lifeform, the group watched as the creature rapidly grew, becoming stronger and able to not only heal itself from damage, but regenerate lost limbs and other body parts.

The "Project Shadow" logo.

However, this success soon proved to be a burden, as the animalistic side of the creature began to grow wild and uncontrollable. Fearful of the implications of the prototype, the leader of the faction of the military organization known as the Guardian Units of Nations - G.U.N. - grew untrusting of Gerald Robotnik. With private information being leaked to the top officials about "Project Shadow," the top brass of G.U.N. soon began brainstorming their own secret plan. Codenamed "ARK's Sealing & Destruction," the intention was to fake a biohazard accident aboard the space colony, evacuating the majority of the residents, in the process using the ruse to seal off "Project Shadow," have Gerald's entire team become "victims" and place all of the blame on the elderly professor.

As the G.U.N. conspirators began to plan their next move, Professor Gerald's next phase in "Project Shadow" was already underway. Proceeding with the data he learned from the prototype's successes and failures, the man of science silently created a more advanced "Ultimate Lifeform," its very genetic structure tied to the powers of the Chaos Emerald. Dubbed "Shadow," the hedgehog-shaped artificial lifeform did not need a life-support system as the lizard prototype did, instead able to do both simple and complex tasks on his own. Along with a far greater intelligence, the black hedgehog took on his own identity, being far closer related to the humans living on the colony than the bestial creature that hid in its lower decks.

Almost immediately, Shadow the Hedgehog befriended Maria, the two becoming constant companions on the ship. Unfortunately, their friendship would prove to be short lived, the G.U.N. forces unable to wait any longer. In an instant, the colony became a war zone, the young girl realizing that her new friend was in danger. Risking everything, Maria escorted Shadow to safety, placing him inside an escape pod. As she wished him farewell, the Ultimate Lifeform could do nothing as he watched the G.U.N. agents burst in, striking her down with a single bullet, her final words echoing in his mind as he plummeted to the planet below...

Shadow the Hedgehog, using Chaos Control.

13 Presidential administrations later, Dr. Eggman, the grandson of Gerald Robotnik, decided to look into his family's past for inspiration, the desire to rule Earth still burning within. Uncovering the forgotten journals of his grandfather, Eggman learned of the botched "Project Shadow," becoming aware that the final results of the project were actually hidden deep within a military base. Powering up a variant of his Eggmobile, Eggman decided to break into Prison Island and uncover its secrets. Typing in a password echoing a tragic loss, the mad genius came across his grandfather's legacy, the living Shadow the Hedgehog, having been trapped for the last five decades in cryogenic stasis. Offering a wish to the doctor, Shadow asked for one thing in return: Chaos Emeralds. With blurred images of past events and broken dreams, Shadow told Eggman to meet him once more on the deck of the now-abandoned Space Colony ARK when he was ready.

Meanwhile, Sonic the Hedgehog, trying to once again enjoy himself, was taken off guard as he found himself unexpectedly arrested by G.U.N. Accusing the hedgehog of not only stealing a Chaos Emerald but also of escaping Prison Island, Sonic found himself handcuffed on the helicopter of unit Sigma Alpha 2. Knowing himself innocent of whatever alleged crime he had been accused of, Sonic broke free from his captors, ripping off part of the wing to the plane and descending onto the capital city below. Once landed, and still escaping from G.U.N.'s forces, Sonic discovered the "fake" hedgehog that he's been mistaken for - Shadow the Hedgehog. Witnessing Shadow using the green Chaos Emerald to perform "Chaos Control," the true blue hedgehog only has one thought on his mind: to clear his name and track down this dark-hued impostor, not knowing that the key to this "faker's" true identity also holds the key for saving the world.

Game Mechanics

Gameplay

As opposed to having each character selectable as in the first Sonic Adventure, the method in which the cast of six are chosen and played was modified to make Sonic Adventure 2 a distinct entity. The player choosing either "Hero" or "Dark," the story is presented with the characters rotating through, each stage having a different character as playable to progress the saga of Shadow the Hedgehog. Because of the duality nature of the game, the three pairs of Hero/Dark share very similar controls and objectives with each other.

As the game can sometimes get confusing, the hint system found within Sonic Adventure returns, but instead of being the calming voice of Tikal the words of wisdom have been replaced with a mechanical being known as Omochao, its features based on the liquid a-life.

Hero Side

Sonic the Hedgehog

Sonic the Hedgehog, once again being the title character, receives the most emphasis in the game, both being central to the plot and in the number of playable levels within the game. Taking most of its cues from Sonic Adventure, Sonic controls in a very similar manner, fully controllable in the 3D world with the use of the control stick. Needing to get from the beginning to the end of the level (sometimes with a time limit, sometimes without), Sonic must traverse the numerous traps, pitfalls, badniks and G.U.N. robots in his path. Once again, the primary jump button becomes the player's most valuable defense in the world of Sonic, a simple push causing Sonic to curl into a ball and jump into the air and performing the spin attack, his spikes becoming the hedgehog's natural weapon. Pressing the jump button twice will once again allow the homing attack to kick into gear, Sonic automatically targeting whatever enemy or other attractable item may be present. The two-button setup also makes a return, the "action" button now having numerous possibilities mapped to it. As more actions become available to the player, an alert in the lower corner of the screen will tell what specific action Sonic will perform when it is pressed. The "y" button on the Dreamcast controller will allow the actions to cycle through, giving the player the option to perform a completely different action than what the game suggests.

The standard function the action button performs when pressed once is the somersault, a new move that attempts to reproduce the function of the basic spin from the classic games, causing Sonic to roll and attack any nearby enemies. This ability also allows Sonic to spin through small openings to allow him to reach other areas of any given level. Pressing and holding the action button causes Sonic to charge up his now-vintage spin dash, the extra time needed to hold the button between the first Adventure and Adventure 2 meant to emulate the time that was spent charging the spin dash in the classic games. Letting go of the button causes Sonic to burst ahead in his curled form, crashing through anything in his way. Other low-key abilities that are mapped initially to the action button are the abilities to pick up, carry and throw items, and the ability to whistle. Though not useful in standard gameplay, whistling can come in handy when exploring the level and finding the occasional pipe sitting in the corner, the whistle sometimes causing an animal to pop out and be picked up for later use in the Chao Garden.

Though not part of the repertoire of actions available by the push of a button, one of the main abilities connected to Sonic (and featured in nearly every Sonic game afterwards) introduced in Sonic Adventure 2 is the ability to grind. Similar to one of the main play mechanics of the Sega game Jet Set Radio, certain surfaces such as rails can now be jumped on by Sonic and, when done so, allow the character to slide across it, accompanied with a grinding sound effect. The grinding ability also becomes an essential part of the scoring system within the game. Though every Sonic title up to this point has had a score connected to the number of subsequent badniks destroyed without hitting the ground, the grind rail provides another scoring opportunity that, when connected with a chain of enemies finished off with the homing attack, can cause up to an extra 2000 points added at any given time.

Just as in the first Adventure, there is once again a plethora of upgradeable items within the game to give Sonic a variety of additional abilities, some familiar and others new. As Sonic Adventure 2 has done away with the Adventure Field, each item in the game is found in one of the levels that Sonic must progress through. The Light Shoes from the first game make a reappearance, located within Metal Harbor. Giving Sonic the ability to use the Light Dash, the hedgehog no longer needs to charge up his spin dash to make use of his new pair of shoes. Instead, a simple tap of the action button is all that is needed to make Sonic follow a perfectly formed trail of rings in his path. The Ancient Light also returns, found hidden in Green Forest. Just as in Sonic Adventure, the Light Attack needs the spin dash charge to be used against a string of enemies, making quick work of them. A total of four new upgrades are also available to Sonic, giving the hedgehog the most in the game. The first of these is the Bounce Bracelet within Pyramid Cave. Giving Sonic the Bounce Attack, the new ability lets Sonic bounce far higher than his standard jump allows, also giving the blue blur the ability to break the ground below him, be it glass or crates. The Flame Ring, found in Crazy Gadget, causes Sonic's somersault to be more powerful, letting the normally unbreakable steel crates in the game succumb to the hedgehog's might. The Magic Gloves located in Sonic's first level, City Escape, can only be reached once Sonic has gotten the Bounce Bracelet and the Flame Ring. Though nothing more than a fun aside, the item allows Sonic to use the Magic Hands ability, enabling the player to turn any nearby enemy into a ball they can carry and subsequently throw. The final item available to Sonic (as well as the other five playable characters) is the Mystic Melody. Hiding out in Final Rush, the magical tune only becomes useful when standing near the various miniature ruins that are hiding within each stage, causing various platforms to appear or doors to open. Though unnecessary in standard game play, it becomes useful during the subsequent "Find the Lost Chao" missions.

The ever-constant ring is still Sonic's most valuable item in the game, collecting them giving Sonic the ability to be hit without losing a life. The fleet of item boxes found in the first Adventure title also make an appearance. Staples such as the extra life, invincibility and speed shoes return, along with the plethora of ring boxes offering five, ten, and twenty rings at any given time. The Jiryoku Barrier is once again available, attracting rings while protecting Sonic from harm. The standard shield is also found within the item boxes hiding out. The explosion item, which destroys all the enemies on screen, can also occasionally be found. Springs, spikes, and Point Markers also come to life, reproducing the effects from their previous outings. However, in addition to marking Sonic's place in the level, the Point Markers also serve to provide Sonic with power-ups, ranging anywhere from rings to speed shoes and shields.

In total, Sonic experiences six stages within the game: City Escape, Metal Harbor, Green Forest, Pyramid Cave, Crazy Gadget and Final Rush. For each, the goal is to reach the Goal Ring, signaling the end and either starting up a boss battle or a new level, most likely with another character and continuing the story.

Miles "Tails" Prower

Miles "Tails" Prower attempting to save Sonic the Hedgehog.

Taking a far departure from his gameplay thus far, Miles "Tails" Prower's controls are far closer to the way E-102 Gamma controlled in the first Sonic Adventure than how Tails behaved in the same game. He is now utilizing the Tornado III (also known as the Cyclone), a new plane that resembles the Tornado II in style and color, but has the ability to change into a biped vehicle form. With a simple press of the action button, Tails can fire his Volkan Cannon, shooting straight ahead in the hopes of hitting an enemy or, more than likely, breaking a crate that may be in his way. Holding down the action button allows the Cyclone to lock on to any nearby target, shooting at them in rapid succession. However, the laser beam used to lock on only lasts for a short amount of time, so if the player continues to hold down, all the targets will disappear, causing the need to start from scratch. Tapping the action button when in front of enemies also allows the Propeller Punch to come into effect, a chained projectile firing from the front of the Cyclone and punching whatever is in the way.

There are also a number of upgrades available for Tails, some of them necessary and others simply to make life easier in the fox's original creation. The first of these is the Booster, found in Mission Street. Pressing and holding the jump button allows the Cyclone to hover, the slow decent necessary to cross over certain pits needed to progress. The Bazooka, a Volkan Cannon upgrade in Eternal Engine, increases the firing power of the mounted cannon, adding the steel crates located about to the repertoire of destroyable items for Tails and his machine. One of the optional upgrades, the Laser Blaster, performs exactly as it did in Sonic Adventure for E-102. Hidden in Prison Lane, it gives the homing missiles the walker shoots out a larger attack pattern, able to decimate more enemies at once. Finally, just as Sonic has access to it, Tails can also pick up the Mystic Melody upgrade. Appropriately found in the Hidden Base, the item performs the same function, giving Tails a tune that will allow the various Knuckles Tribe Pedestals hidden about to perform various functions, used to assist in the "Find the Lost Chao" segments.

Introduced in a cutscene echoing Tails' original scene in the first Adventure, the young mechanical genius goes off to Prison Island to rescue Sonic, who has been recaptured after the events of City Escape. After transforming his ship into the Cyclone upon landing, Tails finds Amy Rose already there, with her own plans on saving Sonic. Telling her to stay out of trouble (which she promptly ignores), the two-tailed fox rushes into the complex, giving players their first taste of this altered control scheme. Though rings are just as important as ever, the Cyclone has a health bar in addition to the ring count. If Tails gets hit without any rings, but the bar still has energy within, the hit will not result in the loss of a life, adding a buffer to the character that did not exist before. The bar, which begins as a dark blue but moves to red when almost finished, can only be replenished with rings. Also, while the variety of item boxes are prominent in Tails' stages, an additional item box with a first-aid kit pictured within can sometimes be found, its effect causing a full restoration of the health bar on the bottom of the screen. The various item box powerups are also scattered through the various levels in an alternate balloon format, either needing a simple shot of the Volkan Cannon or the Cyclone to fly through to let it be activated.

In total, Miles "Tails" Prower shoots his way through four separate levels: Prison Lane, Mission Street, Hidden Base, and Eternal Engine. For each, Tails must reach the Goal Ring at the end of the level, his grade signaling either a boss encounter or the next level staring a different character.

Knuckles the Echidna

Retaining his gameplay from the first Adventure title, Knuckles the Echidna controls in the same basic function as the other characters. With the control stick moving the character about across a three-dimensional plane, the jump button allows the echidna to enter the ever faithful spin attack. Pressing jump twice initiates Knuckles' gliding abilities, letting the player cross large distances as the character slowly descends to Earth. Gliding into a wall, or simply pressing jump twice near one also lets the Guardian of the Master Emerald climb up surfaces. The forward Punch Attack also makes its grand return, either with the simple touch of the action button, or a two-to-three punch combo depending on the number of quick, successive pushes of the button that are done. An additional punching ability has also been included, called the Spiral Upper. By rotating the control stick 360 degrees and pressing the action button, the player can shoot the echidna up in the air, punching whatever may be right above. It also propels him higher than a standard jump. The opposite can also be performed by pressing the same button while Knuckles is gliding, causing him to fire towards the ground as quickly as possible in a fury of strength. As Knuckles goes through various levels that involve interactive water, the ability to swim has been introduced with the echidna. Once only exclusive to Tails in Sonic the Hedgehog 3, Knuckles can jump in water, automatically caught hovering on the surface. Pressing the action button causes the player to dive, the control stick guiding the way, the jump button emulating its purpose by having Knuckles return to the surface. Though sometimes forced to be underwater, it is always important to remember to look out for an air bubble, or to surface often, as Knuckles still needs to breathe else forfeit a life. Being able to pick up items and use the new whistle are also part of Knuckles' repertoire.

A slew of upgradable items, both old and new, are also hidden about the levels Knuckles explores. The Shovel Claw from Sonic Adventure makes a return, letting Knuckles dig into the ground. Digging can happen while standing, while climbing, or by pressing the action button while gliding, letting Knuckles immediately dig at first contact. With the preceding item found in Pumpkin Hill, an item almost nearly as important (though not a necessity) is hidden in Aquatic Mine: the Air Necklace. The necklace lets the player relax while underwater, not having to search for air or surface, the item giving Knuckles an uninterrupted stream of air. The Hammer Gloves located in Death Chamber provide the extra strength necessary for Knuckles to punch through steel containers. This becomes helpful to collect another of Knuckles' upgrade items, the Sunglasses. When found in Meteor Herd, the player can either have them on or off Knuckles' eyes. Aside from simple aesthetics, the glasses prove to have another use: to uncover invisible objects such as springs or item boxes. Though unnecessary in standard play, they become helpful in some of the final missions for each level Knuckles plays through. Finally, the now-familiar Mystic Melody is also an item the echidna can find, hidden in Wild Canyon and useful in the "Find the Lost Chao" missions.

While Tails directly enters the story by looking for Sonic the Hedgehog, Knuckles instead stumbles into the events unknowingly, getting wrapped into everything due to Rouge the Bat stealing the Master Emerald in an unseen encounter. Fighting with the bat girl, they are both taken aback as Dr. Eggman appears from out of nowhere, stealing the Master Emerald himself for no true purpose, but to simply have it in case he needs it down the line. Furious, Knuckles leaps into the air, smashing the emerald to pieces knowing that, because of what occurred in Sonic Adventure, he can collect the pieces and restore it once more. It is not until he meets Sonic and Tails by chance that he gets wrapped up in the larger story involved. Even after this event, though, Knuckles' goal remains largely the same in each level. Just as in the first game, Knuckles must climb, glide, and dig his way through each area trying to find the three pieces of the Master Emerald (or in the case of Death Chamber, the three Eggman keys to continue on with his search). In lieu of the hint orbs from the first game, the ability to find hints as to where the shard locations are is found inside space probes located in each level. Looking more like floating computer screens than anything else, walking over and pressing the action button will cause a hint to show up, slyly pointing as to where the emerald piece could be. The radar at the bottom of the screen also returns, but has been changed significantly. Instead of being able to find all three emerald shards at once, the radar only works for one at a time, meaning the player could be right on top of a piece and not even know it. The reason for this change has been done in terms of scoring: finding a piece quickly (in one minute) and without hints will add an extra 2000 points to your total, while spending longer and using the hints will cause it to move down to 1000, 800, or all the way down to 100 points. Another change is that the signal indicator locks into specific levels now (green, yellow, red).

In total, Knuckles has five levels that he must explore in order to find the Master Emerald pieces (or gate keys in the case of Death Chamber) and restore the item he is sworn to protect: Wild Canyon, Pumpkin Hill, Aquatic Mine, Death Chamber, and Meteor Herd. Only after collecting all three pieces (or keys) in a given level will the game continue on, either entering a boss fight or moving on to the next level featuring a different playable character.

Dark Side

Shadow the Hedgehog

To match with the themes of good versus evil and "Hero" versus "Dark," Shadow the Hedgehog is the playable counterpart of Sonic in terms of control and goals in the game. Using the control stick to move about, the jump button performs the same function, allowing Shadow to curl up into the spin attack and trash whatever foes are nearby. Also able to replicate the homing attack, the action button reveals a similar catalog of moves, both the somersault and the spin dash behaving just as they do for Sonic. Being able to pick up items and throw them, as well as the whistle function, are at Shadow's fingertips.

Each of the four upgrades available to Shadow are also either exactly the same as ones Sonic can receive, or different in name only. The Air Shoes that are hidden in White Jungle serve a similar purpose as the Light Shoes do for Sonic, giving Shadow the ability to perform the Light Dash near a string of rings. Just as Sonic, the dark hedgehog has no need to charge himself up beforehand, being able to simply stand near the collected rings and have the action happen with the push of a button. Found in Sky Rail, the Ancient Light also returns, the Ultimate Lifeform able to replicate the Light Attack and smash through enemies in a new, yet familiar way. The Flame Ring, which was also new to Sonic in this installment, makes its way into Shadow's Radical Highway, letting the G-ordained steel containers break apart as if wood under Shadow's somersault. The final upgrade available, conveniently found in Final Chase, is the Mystic Melody. Helpful in the "Find the Lost Chao" missions, the tune to activate the Knuckles Tribe Pedestals comes just as natural to Shadow as it does the rest of the cast.

Fueled by half-remembered memories and the desire for revenge, Shadow the Hedgehog rushes through four levels total: Radical Highway, White Jungle, Sky Rail and Final Chase. The objective in each is familiar: to reach the end of the level, hitting the Goal Ring to signal the end. Except for White Jungle, each level forgoes having a time limit, and when completed marks either a boss encounter or the next level, a different playable character now in control.

Dr. Eggman

Dr. Eggman in the heart of the G.U.N. fortification.

In an interesting twist, Dr. Eggman behaves in a similar fashion to Miles "Tails" Prower in terms of playstyle within the game. Using a modified Eggmobile dubbed the Egg Walker, the mad genius shares much in common with his earlier creation, E-102 Gamma. With a Volkan Cannon attached to the body, Dr. Eggman is able to swiftly target and shoot whatever may be in his way, more than likely being the forces of G.U.N. trying to stop his plans for world domination and his invasion of their resources. The action button performs the same functions as they do for "Tails," a simple tap shooting out a bullet from the cannon, holding down the button allowing the laser to lock on and shoot missiles at numerous tagets. The time limit for the laser still applies, Eggman's tech not being that much different than what his fox counterpart uses. The jump button also performs the basic action, though because he is in a walker, Eggman is unable to even try and attempt some form of the spin attack. His walker also has its own form of the Propeller Punch, a chained projectile able to knock back whatever moving target might be directly in front of the mad genius.

In terms of upgrades, Dr. Eggman has five available to him during the game, most of them being similar or exactly the same to "Tails." The first, and arguably most important of these, is the Jet Engine, which gives the Egg Walker the ability to hover after jumping in the air, or to hover in case of accidentally falling off the edge, hoping to land on some lower platform and avoid certain death. Located in Lost Colony, it becomes a valuable asset. The G.U.N.-controlled Weapons Bed becomes the scene where the Large Cannon upgrade is found, letting Eggman fire through the steel containers covered in the G.U.N. logo and pick up whatever may be hiding within. Inside Iron Gate is hidden the Laser Blaster, an upgrade which not only Tails gains during the course of his game, but what E-102 Gamma had available to him previously. Just as for those other characters, the upgrade provides Eggman with a larger attack pattern for his homing missiles. The Protective Armor upgrade, however, is one exclusive to the doctor. Found in Cosmic Wall, the armor increases the health bar for Dr. Eggman's Egg Walker, giving it a 1/7th increase. Finally, the Mystic Melody, just as with all the other characters, is locatable for Eggman, this time hiding out in Sand Ocean.

In total, Dr. Eggman has five levels of shooting action: Iron Gate, Sand Ocean, Lost Colony, Weapons Bed, and Cosmic Wall. With a health bar just as Tails possesses, the rings located in each level serve not only as a way to protect the scientific mastermind from harm, but also serve to refuel the bar on the bottom of the screen, letting Eggman suffer through hardship without fear. Reaching the Goal Ring, the level ends, either starting a boss battle or a new level, most likely using a different playable character.

Rouge the Bat

Rouge the Bat looking for the Master Emerald pieces.

Being Knuckles' playable double in Sonic Adventure 2, Rouge the Bat behaves in a similar fashion to everyone's favorite echidna. Pressing the jump button causes an expected result, the female bat lifting off the ground, in the process protecting herself from harm. The action button also reveals a familiar moveset, tapping it not resulting in a punch but a kick, which possesses its own three-hit combo. Twirling the control stick and pressing the action button lets Rouge perform the Screw Kick, firing up in the air and performing the defensive move against what might be sneaking about above her. Pressing the jump button twice initiates her own form of gliding, and even though the character possesses wings which should hypothetically allow her to fly upwards, she is forced to descend slowly. The only way the mysterious treasure hunter can reach higher ground is to climb upwards on a variety of walled surfaces. While gliding, the player can also push the action button to have Rouge fire downwards in a straight line, the Drill Drive ready to smash anything rummaging on the ground.

Just as Shadow and Eggman before her, Rouge the Bat also has a collection of upgradable items which are similar to the upgrades available to her "Hero" counterpart. The first required item, found within the Egg Quarters, is the Pick Nails. When acquired, they give Rouge the ability to dig on the ground, on walls and even use the Drill Dive to automatically dig where applicable. Mad Space's gift to Rouge is the Iron Boots, which let the spy kick her way through steel containers littering the playfield. The Treasure Scope, Rouge's answer to Knuckles' Sunglasses, is found in the Security Hall level. Giving her the ability to see invisible items, the item becomes extremely helpful in the final missions of her given levels. Finally, to round out the cast, the Mystic Melody once again rears its head in Dry Lagoon, Rouge now knowing a tune to make the ancient ruins work for her.

Though given four levels to hunt around (Dry Lagoon, Egg Quarters, Security Hall and Mad Space) only two of these levels possess the same objective as Knuckles' levels: to hunt for the missing pieces of the Master Emerald. While Egg Quarters offers a similar objective to Knuckles' Death Chamber (to collect three items to gain access to Eggman's base), Security Hall's objective is to not find three emerald shards, but three Chaos Emeralds that have been put under lock and key by G.U.N. at some point between the first Adventure and the second, connected to the same facility that held Shadow prisoner. Only after collecting whatever three items Rouge is looking for will the level end, either progressing to a boss battle or to another level with a separate playable character.

Boss Encounters

Due to the structure of the game, the various boss encounters that occur within the game are not perfectly laid out as they were in the classic Mega Drive titles, nor are they obviously laid out as they were in the first Sonic Adventure. Sometimes happening before a level, sometimes happening after one is finished, and sometimes not happening between a level at all, the boss battles are varied in placement but similar in style. Most of the boss battles are shared between the "Hero" and "Dark" stories, the majority involving fights between the paired Hero/Dark playstyles. In both, Sonic/Shadow, Tails/Eggman and Knuckles/Rouge face off against each other at some point, the first two fighting twice, the last pair only once. Because of the similar nature of the characters in terms of control, the battles can sometimes be difficult, other times evenly matched. The only boss battle that is shared by the two stories that is not a direct fight between the playable characters is the Egg Golem, which is also the only boss in the entire game that is built by Dr. Eggman. For this fight which happens in Eggman's pyramid base, both Sonic and the doctor are forced to fight, one taking place right after the other.

There are also two boss fights in each main story that are unique, although three of them are G.U.N.-based, and thus have very similar physical structures. The fourth, which is an exclusive boss encounter with Knuckles, is a fight with King Boom Boo. With its day/night fight strategy, the entire battle stands out in the game, being completely different from anything else presented to the heroes or villains.

Kart Racing

Returning from the first game, the Kart Racing segments of the game have been slightly expanded this time around. While still a selectable mode that can be played through in the traditional three-lap circuit, the use of the racing mechanic in the main body of the game has been increased. In Sonic Adventure'sTwinkle Park, the kart section was relegated to the first half of the level, the only goal being to get to the end without falling off the track or crashing into an enemy with no rings. In Sonic Adventure 2, however, both Tails and Rouge are given their own separate level during their respective stories in which they must chase after a moving target. For "Tails," his goal is to follow the President's limo before he leaves the city limits, following behind in his Tornado III now in a vehicle mode unused in the rest of the game. Rouge, meanwhile, follows Tails as he flies in the Tornado III, keeping track of his movements for Shadow and Eggman. Instead of simply reaching the end of the track being the objective, a timed component is used, similar to the arcade-style racers of Sega and other companies. Split up into three parts, the character must reach the goal line for each segment before the timer runs out, else risk losing a life and having to begin the race again. Having to dodge other vehicles, avoid crashing into walls and trying to be in line with speed boosters and the occasional balloon containing extra time, the racing segments become deceivingly hard when compared to the rest of the game.

Last Story/Super Sonic

Once both the "Hero" and "Dark" stories are successfully completed, a final "Last" story becomes unlocked on the main screen. When chosen, the two story threads finally intertwine, revelations of the true nature of "Project Shadow" finally coming to light. Although Eggman clearly tried to stop Perfect Chaos on his own in the finale of the first Sonic Adventure, this is the first time in a Sonic game when Dr. Eggman is forced to work side-by-side with Sonic and Tails in an effort to stop his grandfather's actual plan. The story is only composed of one level - Cannon's Core - and two boss battles. The level is broken up into five separate parts, each played through by one of the main characters, beginning with Tails and ending with Sonic. The odd one out is Shadow, who for story purposes chooses to remain outside of the battle until confronted by Amy Rose, who sparks the return of forgotten promises. Filled with a new sense of purpose, Shadow alone fights the first boss in the final story, the "Prototype of the Ultimate Lifeform," Biolizard.

The final boss is fought with both Sonic and Shadow who have transformed into Super Sonic and Super Shadow, respectively. Having the final battle take place in space, the duo must switch off as they try and finish off Finalhazard, the switching between the two characters the best way to replenish the ring counts of both. Using the control stick to move about the screen, the jump button is used as a sort of dash which can blast ahead, striking the weak areas of the uncontrollable lizard, enacting damage against it. As the Chaos Emeralds are once again used heavily in the story and not collectible in any Special Stage, the ability to turn super is relegated to the final boss only.

Stage Select

After completing a level in the main game, the option to play through it at the player's leisure becomes available through the stage select menu. Displayed in a simple map of the game's areas, each stage (including the two racing levels and the Chao Garden) can be toggled through and chosen. When one of the levels is selected, a secondary menu appears. While the central mission of each in the story mode can be replayed, four additional missions for each stage are also selectable, vastly increasing the replayability of the game. The additional four missions for each standard zone include collecting one hundred rings, finding a lost Chao in the level, beating the stage in a specific time limit, and finally reaching the end in a "hard mode" version of the level. For the two Kart-based levels, the Chao and Time Limit missions are replaced with going through the course and not touching either the walls or the other cars.

In addition, the stage select menu also keeps track of the lettered grade that is awarded at the end of each run, ranging from a perfect "A" to a less-than-desirable "E." As each level and mission has its own requirements to reach an "A," only practice and determination can award the most dedicated at finishing each and every stage with perfection. It should be noted that, within each stage, a Gold Beetle is hidden somewhere within, and only appears for a few seconds. If broken, an extra 1000 points is added to the total, which can come in handy in trying to reach those illustrious "A" rankings.

Chao

Sonic Adventure 2 also sees the return of the Chao, the small, water-shaped A-life first introduced in the game's predecessor. For the sequel, the entire Chao raising experience has been completely revamped and expanded. As there are no Adventure Fields to speak off, the only way to enter the Chao Gardens in the main game is to find one of three Chao Containers located in each level, the first always holding a Chao Key. With the key in the player's possession, at the end of the level the player is warped to Chao World, the portal to the rest of the Chao experience in the game. Though at first only the standard Chao Garden is available, as time in the garden goes on, a "Hero Garden" and "Dark Garden" also become available. To also play off the Hero/Dark aspects of the game, the Chao's that are raised also have the potential to either be halo-wearing Hero Chao, or the devilishy-cute Dark Chao, depending on the characters that end up raising them.

Chao Racing also returns in full gear, with an expanded set of races the assorted Chao can go through. Having Neutral, Hero, and Dark races, the race selection screen can only be accessed through the Neutral Chao Garden.

In addition, a mode called the Chao Kindergarten is added to the raising process. Available right off the bat, the Kindergarten offers tips and tricks on how to raise your Chao, a classroom where Chao can learn new skills and a Chao Doctor that can check up on your Chao and tell you specific information on its health and habits.

Two Player Mode

Just as Sonic the Hedgehog 2 did for the 2D games, Sonic Adventure 2 was the first 3D Sonic game to have a fully-formed two player mode available. Not including the Kart Racing, the three options for play are split up in the Hero/Dark playstyles. The first of these has one player controlling Sonic and the other Shadow as they race against each other in one of the character's stages, the first to reach the end being the winner. The second of these, the Tails/Eggman stages, closely resemble the boss battles between the two, fighting in an arena until one of the pair loses the energy in their mechanical walkers. The third choice, Knuckles/Rouge, is a competition to see who can get two of the three Master Emerald pieces first.

As an extra bonus, six extra unlockable characters are available in the two player mode, awarded after collected all "A" ranks with a given character in the regular game. For Sonic and Shadow, the characters are Amy Rose and Metal Sonic respectively. For Tails and Eggman, a Chao in a Chao Walker and Big the Cat become playable characters. Finally, for Knuckles and Rouge, Tikal and Chaos are unlocked as playable characters in the two-player mode.

Emblems

In total, 180 emblems are available in the full game, connected to a variety of tasks. Completing each story, finishing each mission for every level, and playing through a boss rush for each side unlock emblems, as well as a number connected to the Chao Racing portion of the game. Unlike Sonic Adventure where the emblems were only for bragging rights, collecting every emblem (and achieving an "A" rank on every stage) will unlock the extra level Green Hill. A three-dimensional recreation of the first act of the original Green Hill Zone from Sonic the Hedgehog, the level is meant to be a celebration of Sonic's tenth anniversary, which happened to coincide with the release of Sonic Adventure 2.

Score

The total score, when it exists (missions 1, 4 and 5), is the base score achieved while playing the level plus the time bonus upon mission conclusion.

variable points per enemy destroyed in a row, variable trick points awarded for Sonic and Shadow (platform jump trick, end of rail jump trick if going at enough speed, plus an unsorted amount usually tied to each level) and time bonus per treasure for Knuckles and Rouge.

Note: Since Route 101 has no Lost Chao and is an already timed mission, for mission 3 and 4 it's required that the player doesn't touch any cars and walls respectively. Also, as its time limit in hard mode is 2:50, none of the rankings below A are actually possible on that mission.

Note: Since Route 280 has no Lost Chao and is an already timed mission, for mission 3 and 4 it's required that the player doesn't touch any cars and walls respectively. Also, as its time limit in hard mode is 3:25, none of the rankings below B are actually possible on that mission.

All regional versions of the game feature options to switch the voice language into Japanese and English and the text language into Japanese, English, German, French and Spanish. The downloadable 2012 version also added Italian text language.

Game revisions

When being ported to the Nintendo GameCube, several additions were created for Sonic Adventure 2: Battle. The most notable of these changes was an expanded two player mode. While in the Dreamcast original only a handful of levels were available for play, nearly every level was added to the GameCube version, making the choices far more robust. Many of the downloadable additions to the original were also included on the port, either from the get-go or by unlocking them during play, including the ability to use Eggrobo in the Kart Racing sections. Various graphical changes and enhancements are also littered about, some more noticeable than others. One of the more baffling changes, however, stems from one of the major easter eggs in the Dreamcast version. Hidden somewhere in each level was a model of Big the Cat caught up in sometimes dangerous, sometimes humorous situations. When the game was ported, nearly all of these cameos were removed replaced instead with rings for some unknown reason. Although occasionally Big the Cat can show up when certain buttons are pushed during cutscenes, the character was also removed as an unlockable two player skin, replaced with a Dark Chao instead.

Rereleases

Adaptations

The Sonic Adventure 2 story received a curious adaptation in the pages of Archie Comics, Sega telling the company to adapt the game even though the writers at the time weren't prepared to tell the story. Dedicating issue #98 to the game, the comic served only to adapt the initial backstory of Dr. Eggman coming across Shadow and Sonic's mistaken arrest, the end of the story telling readers to play the game to find out how the story ends. Because of the discrepancies between the Archie universe and the games, many readers were unsure just what was meant to have happened in the comic proper. It wouldn't be until years later in the pages of Sonic Universe #2 that the rest of the game would be adapted in the pages of the Archie comic. The game was also later adapted into a story arc of the animated series Sonic X, starting with episode 33 "The Puzzle of Project Shadow" and culminating in episode 38, "Maria's Request, Everyone's Request." Of note is the fact that, in adapting the game to the airwaves, the series-specific character Chris Thorndyke ends up replacing Amy Rose's part in key portions of the tale, including aboard the Space Colony ARK when Shadow finally remembers the true promise he made to Maria.